The following blog post is from the website EntryTestPreparation.com and it states aspects of prefixes which might be tested. There isn't much else on this website about Physics, but I thought that the bit about prefixes was summarized well.

Table of prefixes

On the basis of exponent of ten the prefixes can be divided into two categories.i) having a positive exponentii) having a negative exponent

So what type of questions can be asked from this table?

1) You can be given a name of the prefix or symbol and can be asked which value does it represent or vice versa

2) You can be given a name of the prefix and can be asked about its symbol and vice versa

3) You can be asked questions like:

Capital alphabets are used as symbol for which type of prefixesa) With exponentsb) With negative exponentsc) Bothd) none

Same question can be asked for small alphabets.

The above question can also be asked in the converse manneri.e.Positive exponents are used for prefixes whose symbols area) capital alphabetsb) small alphabetsc) bothd) none

4) You can be asked how much time one prefix is the othere.g.How many kilos make one tera?

Order of Magnitude:

The order of magnitude of a number is the power of ten when the number is expressed in scientific notation.For example, if F = 5 x 10^7 and G= 9 x 10^6, then the order of magnitude of F is 7 and B is 6.

This term can be used in the tests, although not mentioned in the text books but should be known.